Headstock quill for cylindrical grinder



Sept. 24, 1968 H. MAACK 3,402,513

HEADSTOCK QUILL FOR CYLINDRICAL GRINDER Filed May 20, 1966 2 Sheets-Sheet l illll filllllllllllll"ml!" IN\-ENTOR. Horst MQGCK M v y 1 03 o %co ATToRNEYs Sept. 24, 1968 H. MAACK 3,402,513

HEADSTOCK QUILL FOR CYLINDRICAL GRINDER Filed May 20, 1966 2 Sheets-Sheet 2 United States Patent 3,402,513 HEADSTOCK QUILL FOR CYLINDRICAL GRINDER Horst Maack, Cincinnati, Ohio, assignor to The Cincinnati Milling Machine Co., Cincinnati, Ohio, a corporation of Ohio Filed May 20, 1966, Ser. No. 551,582 6 Claims. (Cl. 51-165) ABSTRACT OF THE DISCLOSURE A precision cylindrical grinding machine headstock mechanism is disclosed and described herein. The mechanism includes an axially positioned center member to shift a workpiece to a proper position for grinding and to rotatably support the workpiece during a grinding operation. Shifting of the center member is produced by a rotary power input to drive an orbiting gear mechanism that in turn rotates a cam that determines the axial position of the center member in the headstock.

The present invention is intended to be used in a precision center-type cylindrical grinding machine of the type wherein the workpiece must be both radially and axially positioned prior to grinding and then be firmly held in position against both radial and axial forces during a grinding operation. A machine having a wheelhead movable along ways transverse to the axis of the work but at an angle other than a right angle in which both cylindrical portions and shoulders are ground at the same time is an example of this type of machine. Machines of this type are provided with one center to initially engage the work and to push it into contact with the other center which then is moved back toward the one center until the workpiece is in the proper axial position as determined by an automatic gauging device. Many types of machines such as these are available and well known in the machine tool industry. Both centers thereafter cooperate to support the workpiece during the grinding operation. Since the one center that first engages the workpiece must yield as the other center is shifted axially to position the work, this one center is normally provided with a spring biasing mechanism tending to move it toward the other center. It is not satisfactory to grind toward this spring biased center as the forces of grinding are not accurately predictable and often exceed the forces provided by reasonably sized spring. Therefore it is the usual practice to arrange the grinding operation so that the forces act in the axial direction toward the center which is powered to axially locate the work prior to the actual grinding operation. This center must then hold firm against these forces. To accomplish this it has sometimes been the practice to clamp the axial positioning center after the work is in place for grinding but this has a tendency to cause the center to be moved out of proper axial alignment and to cause the work to be rotated on a slightly skewed axis during grinding with the result that tapered or irregular workpieces are produced.

It is therefore one object of this invention to provide a grinding machine center with a positioning mechanism which will not yield before the axial forces of grinding and yet is one in which no clamping or locking mechanism is required or included.

It is also an object of this invention to provide an improved axial positioning drive for a grinding machine center which provides exceptionally smooth movement and which is automatically reset upon overtravel without reversing the direction of power input and without backlash becoming a factor in its accuracy.

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It is yet another object of this invention to provide an axial center positioning mechanism in a grinding machine headstock which visually displays for the operators convenience the extent of positioning movement.

It is a further object of this invention to provide a small mechanism that can be included in even a small grinding machine headstock but which has sufficient power and accuracy of movement to perform well to very exact tolerances.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

In its preferred form, this invention utilizes'a uni directional power source to produce the axial movement of a work supporting a center in a grinding machine. The mechanism includes a speed reducer to get uniform and forceful movement with a relatively small but high speed power source. The mechanism also employs a cam to convert the unidirectional power input to a slow positioning movement in one direction and a relatively rapid retraction movement in the other direction in the case of over travel without requiring an interruption or reversal of the input drive from the power source. The use of the cam also provides the irreversible drive that is necessary to hold against the axial forces of grinding after the workpiece is located. The mechanism operates to move the work holding and locating center through a uniform reversible stroke and a mechanism is included in the system to provide the machine operator with a visible representation of the exact instantaneous position of the center member within its range of axial movement. This enables the operator to detect repeated location of the center near one or the other of the two axial extremes of movement in which case he would then shift the entire headstock to such a position that the final axial positioning of a workpiece would occur with the center near the middle of its axial stroke.

A clear understanding of this invention can be obtained from the following detailed description in which reference is made to the attached drawings wherein:

FIG. 1 is a front view of grinding machine headstock partly in elevation and partly shown in section.

FIG. 2 is a longitudinal section view of the mechanism within the headstock of FIG. 1 showing the mechanism by which its center member is axially moved.

FIG. 3 is a partial side elevation of the headstock as viewed from line 3-3 of FIG. 1.

The present invention is illustrated in a specific embodiment in FIGS. l-3 to provide an axial stroke of a head stock center 9 useful in axially positioning a workpiece (not shown) in a precise position prior to grinding as is a common practice in automatic cycle grinding operation. The center 9 is a dead center in that it does not rotate during a grinding operation. The workpiece supported at one end by the center 9 is rotatably driven by a driver dog 10 that extends from a driving ring 11 which is rotatably supported on the side of the headstock unit 12 and through which the center 9 extends. The center 9 is held in a holder member 13 that slides axially through a sleeve 14 which is fixed in position in the headstock 12. The center holder 13 is axially movable and therefore it is provided with two bearing lands 15, 16 at its ends inside the sleeve 14. Lubrication grooves 17 are formed in these lands 15, 16 to insure that they are maintained movable since the clearance between the lands 15, 16 and the sleeve 14 must be kept at an absolute minimum to provide a rigid support for the center holder 1 and center 9.

The center 9 and holder 13 are axially moved under power furnished by a rotary drive motor 18 that is supported by a housing 19 secured onto the headstock unit 12 at the side opposite the drive ring 11. The mechanism within the drive housing 19 and its connection to the center holder 13 is shown in the sectional view of FIG. 2. The rotary drive output from the motor 18 is transmitted from a pinion 20 to an idler gear 21 that is rotatably mounted on a stub shaft 22 in the housing 19. The gear 21, in turn, is in mesh with a gear 23. The gear 23 is received over a sleeve 24 and is retained thereon by a shoulder 25 and a snap ring 26. A key 27 is received between the gear 23 and the sleeve 24 to render these two members rotatable in unison. The sleeve 24 is held inside the housing 19 by a pair of roller bearings 28, 29 so that it is rotatable therein on an axis that extends through the center 9 on its centerline. Therefore, the sleeve 24 is rotatably driven by the motor 18 when that motor is energized.

A flange 30 is provided at the forward end of the sleeve 24 and a gear 31 is rotatably supported by a roller bearing 32 on an axle 33 therein so that the gear 31 is rotatable on an axis parallel to the axis of rotation of the sleeve 24. The teeth of the gear 31 extend radially outward from the flange 30 and are in axial alignment and in mesh with a pair of gears 34 and 35. The gear 34 is formed directly in the housing 19 and is therefore stationary. The gear 35 is formed on the rear face of a cam member 36 that is rotatably received over a journal member 37 on the rearward end of the center holder 13. Thus the gear 35 is rotatable within the housing 19. The gear 35 has one tooth more than the gear 34. As the small gear 31 is rolled around the stationary gear 34 and the movable gear 35 upon rotation of the sleeve 24, the gear 35 will be rotated through one tooth spacing with respect to the fixed gear 34. This structure provides an orbital drive mechanism giving a great reduction of speed in the rotational drive between the sleeve 24 and the cam member 36.

The cam member 36 has a face 38 that is shaped to provide a constant or linear rise around in one direction from a low point to a high point. This high point is angularly spaced only a few degrees from the low point in the other direction. Thus, in moving completely around the face 38 in the one direction a gradual rise in the axial dimension of the cam 36 occurs until the peak is reached at which time continued movement in the same direction results in a quick fall back to the starting point. The face 38 is engaged by a roller 39 that is mounted on an axle 40. The axle 40 is carried in a collar 41 on the rearward end of the center holder 13 and is secured in place both by pins 42 and the axle 40 itself, since it extends into the center holder 13. The collar 41 also carries a pin 43, shown angularly out of position, which extends into a radial slot 44 in the rear face of the sleeve 14. The sleeve 14 is fixed in the housing 12 by machine screws (not shown) and therefore the pin 43 functions as a key to prevent the collar 41 and holder 13 from rotating. The slot 44 is deeper than the exposed length the pin 43 and therefore the pin 43 can move into the slot 44 to allow axial movement of the holder 13 and collar 41.

The collar 41 also carries a set of axially extending members 45 that are fixed thereon by machine screws 46 and the members 45 are spaced around the for-ward face of the collar 41. Each of the members 45 extends into a recess 47 in the rear face of the sleeve 14 where it is forcefully engaged 'by a stack of spring washers 48 that tends to move the collar 41 and holder 13 axially rearward. Rearward movement of the collar 41 is stopped by the cam 36 that is engaged by the roller 39 carried in the collar 41 as described. Rearward movement of the cam 36 is prevented by the sleeve 24 which, in turn,

is held in axial position by its flange 30. Since the cam 36 and sleeve 24 are relatively rotatable, a thrust hearing 49 is embraced therebetween to transmit the axial forces only. Also, the sleeve 24 is rotatable in the housing 19 and therefore a thrust bearing 50 is provided to transmit the axial forces between these two members that result from the transmission of the rearward forces on the holder 13 and collar 41 to the sleeve 24.

A sleeve extension 51 is fixed onto the cam member 36 by machine screws 52 and this extension passes through the sleeve 24 to the rear of the housing 19. The extension 51 is rotatably supported in the sleeve 24 by bearings 53 and 54. The rearmost end of the sleeve is exposed as shown in FIG. 3 and is provided with a reference mark 55 which gives an indication of the angular position of the sleeve 51 and the cam 36 within the housing 19. A dial 56 is secured on the back of the housing and this is provided with markings 57 corresponding to the axial rise at various angular positions around the cam 36 from the zero or lowest position which is in alignment with the reference mark 55. The sleeve 51 also has a ring 58 fixed thereon by a set screw 59 and the ring 58 carries a pin 60 that extends to engage the operator arm 61 of a limit switch 62 when the sleeve 51 is in the angular position corresponding to the engagement of the roller 39 with the lowest point on the cam face 38, that is, when the holder 13 is in its rearmost or retracted position in the sleeve 14. This limit switch 62 provides a control signal useful in automatic operation of a grinding machine by providing the control system with information as to the extended or retracted condition of the holder 13 and center 9.

From this construction it can be seen that energization of the motor 18 will cause rotation of the cam 36 at a rate greatly reduced from the motor output rate. The rotation of the cam 36 will cause the holder 13 to shift axially outward in the sleeve 14 until the high point of the cam face 38 is reached. Continued rotation will cause a rather quick retraction of the holder 13 and center 9. The visual display of this movement in convenient form will be available at the rear of the housing 19. The system shown is to provide an advancing of the center 9 through a 0.09 inch stroke. Approximately 300 degrees of rotation of the cam 36 and sleeve 51 in the clockwise direction, as viewed in :FIG. 3, is required to provide this amount of advance. The continued clockwise movement through the next 60 degrees retracts the center 9 and resets the system in its retracted position. The slowly rising portion of the cam 36 provides an irreversible drive for the center 9 which will resist very high axial loading forces from the center 9 and holder 13 without yielding. Therefore no clamping mechanism is required in the mechanism to operate after the center 9 is positioned.

The mechanism is also provided with convenient means for displacing the center 9 from the holder 13. The center 9 is provided with a conventional sticking taper shape which is adapted to mate with the tapered internal socket formed in the holder 13 and in this manner is retained in a fixed position therein. A substantial force is required to force the center 9 out from the holder 13 and in the mechanism described, a bar 63 is provided to produce this force. The bar 63 is movable in the sleeve 51 both axially and rotatably. It has a threaded portion 64 engaged through mating threads in the rear of the holder 13 and extends forward therefrom to a position close to the rear of the center 9. The rearmost end of the 'bar 63 is exposed at the rearward end of the sleeve 51 and is provided with a hexagonal socket 65 by means of which a rotary force may be coupled to the bar 63. Rotation of the bar 63 causes it to move axially by reason of the threaded portion 64 and it can therefore be moved forcefully against the center 9 to force it out.

being rotatable relative to said first drive member and concentric with the center member and an orbiting member operable to transmit a rotational drive be tween said first and second drive members, and

(b) said cam is integrally attached to said second drive What is claimed is:

1. In a grinding machine headstock having a center member supported therein for axial movement, a mechanism for axially positioning the center member comprismg: 5

(a) a motor operable to produce a rotating power out- (b) an orbital drive speed reducer transmission mechanism,

(c) a cam connected to said motor by said transmismember and the face thereof is concentric with the center member. 5. The grinding machine headstock of claim 4 wherein: (a) a sleeve member is received in the headstock for axial movement therein and is coaxial with said cam sion mechanism and rotated thereby at a speed great- 10 face, ly reduced from that of said motor and having an (b) the center member is attached in said sleeve memannular face therearound progressively rising in one her and extends outward from one end thereof, direction from a low point to a high point and sub- (c) means are provided preventing rotation of said sequently falling relatively sharply back to said low sleeve member, point to complete the circuit thereof, and (d) a roller is attached to said sleeve member at the (d) means for shifting the axial position of the center end opposite said one end thereof, and

member in accordance with the contour of said face (e) said bias means produces a force tending to shift upon rotation of said cam by said motor. said sleeve member into the headstock to hold said 2. The grinding machine headstock of claim 1 wherein: roller against said cam face. (a) said cam is rotatable in a fixed position in the 6. The grinding machine headstockofclaimS wherein: headstock, (a) said one end of the sleeve member extends to (-b) said means for shifting includes bias means prothe forward end of the headstock to hold the center ducing a force tending to move the center member member exposed thereat, inwardly in the headstock against said cam face, and (b) an annular dial is attached at the rearward end of (c) said motor rotates said cam to produce a force in the headstock opposite the forward end,

opposition to and greater than the force of said (c) a sleeve extends rearward from said second drive bias means to shift the center member outward from member and through said first drive member and said the headstock during a portion of each revolution of annular dial and is provided with a reference mark, said cam, said outward movement corresponding in said sleeve being rotatable with said second drive range to the rise of said cam face from the low point member, and to the high point thereof. (d) calibrating marks are provided on said dial and 3. The grinding machine headstock of claim 2 wherein: cooperate with said reference mark to display the in- (a) adial is provided having calibrations in accordance stantaneous axial position of said sleeve and center with the range of movement of said center member, members in the headstock. and (b) means are provided for indicating relative to said References Cited dial the instantaneous position of said center mem- UNITED STATES PATENTS lber Within the the range 0f movement thel'fiof. 2 955 391 10 19 0 Fred 51 237 X 4. Thegnnding machine headstock of cla1m 2 where n: 40 3,064,395 11/1962 Price 51 237 X (a) said speed reducer transmlssion tmeohanlsm 1n- 3,290,833 12/1966 Baker 51 165 cludes a planetary mechanism including first and second drive members, said second drive member LESTER M. SWINGLE, Primary Examiner. 

